• Korean Journal of Materials Research
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• 제16권5호
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• pp.277-284
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• 2006

The alloys were prepared by a non-consumable vacuum arc melting and homogenized at $1050^{\circ}C$ for 24 hrs. Two kind of surface modifications were performed alkali treatment in 5.0M NaOH solution subsequent and heat treatment in vacuum furnace at $600^{\circ}C$, and were oxidizing treatment at the temperature range of 550 to $750^{\circ}C$ for 30 minutes. After surface modification, these samples were soaked in SBF which consists of nearly the same ion concentration as human blood plasma. Cytotoxicity tests were performed in MTT assay treated L929 fibroblast cell culture, using indirect methods. A porous and thin activated layer was formed on Titanium and Ti-8Ta-3Nb alloy by the alkali treatment. A bone-like hydroxyapatite was nucleated on the activated porous surfaces during the in vitro test. However, Ti-8Ta-3Nb alloys showed better bioactive properties than Titanium. According to XRD results, oxide layers composed of mostly $TiO_2$(rutile) phases. Cytotoxicity test also revealed that moderate oxidation treatment lowers cell toxicity and Ti-8Ta-3Nb alloy showed better results compared with Titanium.

• Analytical Science and Technology
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• 제5권3호
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• pp.319-325
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• 1992

Plasma are melting method was used in making Mo-1.17 Ti-0.18 Zr-0.06 C ingot having over 99% of the theoretical density. Oxygen content herewith, decreased from the origin of 830ppm to 40ppm. After cold rolling of Mo alloy by 50%, the recrystallization behaviors were studied in the temperature range from $800^{\circ}C$ to $2100^{\circ}C$ for 1 hr isochronical holding time and also at $1400^{\circ}C$, $1500^{\circ}C$, $1600^{\circ}C$ for varying isothermal holding time 0 to 108000sec. The complete recrystallization temperature of Mo was $1400^{\circ}C$ but that of Mo alloy was $1700^{\circ}C$. 50%-1 hr recrystallization temperature of Mo alloy sheet was about $1500^{\circ}C$ and when compared to Mo there was an increase of over $300^{\circ}C$. The activation energy of recrystallization of Mo alloy sheet was 508kJ/mol.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2003년도 High Temperature Superconductivity Vol.XIII
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• pp.64-64
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• 2003

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2004년도 High Temperature Superconductivity Vol.XIV
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• pp.83-83
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• 2004

• Proceedings of the KWS Conference
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.40-42
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• 2003

In general, nickel-base superalloy has been extensively used as land-based gas turbine blades and vanes. Plasma transferred arc welding(PTAW) has been considered as a repair welding process of nickel-base superalloy. This research evaluated the relationship between hot ductility behavior and hot cracking susceptibility in nickel-base superalloys. Ductility recovery rate of nickel base superalloys was found to be poor due to incipient melting and constitutional liquation. This seems to increase the hot cracking susceptibility.

• Journal of the Korean Society for Heat Treatment
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• 제8권1호
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• pp.84-88
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• 1995

Various heat-treatments were conducted to Ti-48.1at%Al and Ti-48.3at%Al-1.2at%Mn alloys casted by plasma arc melting system. Mechanical properties, microstructure and high temperature oxidizing behaviors of as-casted and heat-treatment alloys were investigated. Ti-48.1Al and Ti-48.3Al-1.2Mn alloys were decreased in strength according to increased of heattreatment temperature. Oxidizing weight gain of Ti-48.1Al alloy which conducted at $1273^{\circ}K$ was linearly increased. In case of adding Mn to alloy, there was no rapid increase of oxidizing weight gain during early time.

• Journal of the Korean institute of surface engineering
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• 제25권5호
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• pp.253-261
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• 1992

Ti-Al intermetallic compounds which can be used in gas turbine at elevated temperature were inves-tigated in order to improve oxidation resistance by the formation of protective oxide scale. Four Ti-Al alloys were prepared by plasma arc melting. As the amount of Al was increased among the alloys, oxida-tion resistance was improved by the formation of relatively purer Al2O3 layer. However, the alloys which have less amount of Al formed a duplex layer of Al2O3 and TiO2. When samples were oxidized in pure oxygen instead of air, oxidation resistance was improved because of formation of the purer Al2O3 layer.

• Resources Recycling
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• 제7권5호
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• pp.19-25
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• 1998

High temperature thermal behaviors of EAF dust by coke at initial reaction stage were studied to obtain the fundamental data of EAF dust treatment process, that is Extended Arc Plasma Furnace System called RAPID system. In this study thermal behaviors including calcination of limestone, devolatilization of EAF dust itself, and reduction & devolatilization of mixture(EAF dust : coke : limestone = 80 : 10 : 10 wt.%) were investigated as functions of reaction temperature (1000~1300$^{\circ}C$) and reaction time (3~12 min), considering the 180% equivalence of carbon reduction and 1.7 bacisity for optimum reduction and melting of EAF dust in the RAPID system. Size of sample was about below 0.1 mm for these experiments. Limestone was completely calcined at above 1100$^{\circ}C$ within 1 minutes. In the case of devolatilization of EAF dust itself, weight loss of EAF dust was about 14% at 1300$^{\circ}C$ and 12 minutes, and partial sintering and melting were found in part of sample. Weight loss of mixtures increased with increasing reaction temperature and time, about 46% weight loss in it was occurred at 1300$^{\circ}C$ and 12 minutes. From these weight losses showing devolatilization and reduction of EAF dust, the treatment time of EAF dust inside.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제17권1호
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• pp.94-100
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• 2004

We fabricated textured Ag substrates for YBCO coated conductor and evaluated the effects of annealing temperature on microstructural evolution, texture formation, and surface morphology. Ag ingot, as an initial specimen, was prepared by plasma arc melting(PAM). Subsequently, the ingot was cold rolled to 100 ${\mu}{\textrm}{m}$ thick tape and annealed at temperatures of 600-80$0^{\circ}C$. The texture and surface morphology of the substrate were characterized by pole-figure and atomic force microscopy(AFM) profile, respectively. It was observed that a strong ｛110｝<110> texture was formed after annealing and its symmetry improved as annealing temperature increased. The full-width at half-maximum(FWHM) of ｛110｝<110> pole was as sharp as 10$^{\circ}$ for the substrate annealed at 80$0^{\circ}C$. On the other hand, it was found that the thermal grooving and faceting became remarkable as annealing temperature increased : root-mean-square(RMS) roughness of the substrate annealed at 80$0^{\circ}C$ was 39.2 nm. The substrate of strong texture and smooth surface, fabricated in our study, is considered to be suitable for use as a substrate for the epitaxial deposition of superconductor film.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.50.1-50.1
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• 2010

내열성과 내부식성, 촉매능력등이 뛰어난 백금은 자동차 배출가스 정화촉매, 유/무기화학반응의 공정 촉매, 석유화학산업에서의 촉매 등 촉매 뿐만 아니라 용융유리용 도가니, 유리 섬유용 부싱 등의 유리산업, 백금 열전대 외에도 전기/전자기기, 치과용 합금, 장신구, 항공우주,등의 많은 분야에서 폭넓게 쓰인다. 한편 낮은 기계적 특성을 개선하기 위하여 로듐 등의 백금족 원소를 첨가한 합금을 제조하여 이용하고 있지만 로듐의 공금 부족과 이에 따른 가격 상승으로 인한 대체조성의 설계가 요구되고 있다. 또한 고온의 산화분위기에 노출이 되면 산화물이 형성되고 이것이 휘발하여 중량의 손실이 생긴다고 알려져 있다. 본 연구에서는 백금 합금의 이러한 문제점의 해결방안을 제시하고자 백금족 원소를 첨가하고 첨가 원소별 산화휘발의 정도를 측정하였다. 시편은 plasma arc melting법으로 각각 Pt, Pt-20%Rh, Pt-11%Ir, Pt-10%Rh-10%Ir의 조성을 가지는 합금을 만든 후 압연을 하여 판상으로 만들었고, 이를 각각 $1000^{\circ}C$, $1200^{\circ}C$, $1400^{\circ}C$ 등에서 각각 96시간 까지 산화휘발시켜 중량손실량을 측정하였고 이를 XPS를 이용한 표면분석을 하여 산화휘발거동을 규명하였다. 그 결과 Pt-20%Rh가 가장 우수한 고온산화휘발특성을 보였으며 상대적으로 고온산화휘발특성이 좋지 않은 Pt-Ir 2원계 합금에 Rh를 첨가한 Pt-10%Rh-10%Ir 3원계 합금을 만들어 약 60% 향상된 결과를 얻을 수 있었고 이 결과를 증기압 관점에서 고찰하였다.